The group said it was unlikely those problems were related to the vaccine, but said the issues should still be noted on the product labeling.

“This wasn’t a pregnancy trial and it wasn’t meant to be used in pregnancy, it just happened accidentally,” said Dr. Kenneth Noller, of Tufts University. “I think this could be marketed with the usual caveat that it’s not to be used in pregnancy.”

The human papilloma virus, or HPV, infects about 6 million people in the U.S. each year, and is mainly spread through sexual contact. It usually doesn’t carry any symptoms and goes away within two years, but rare cases can develop into warts and cancers in both men and women.

Last year, nearly 4,000 women died of cervical cancer in the U.S., less than 1 percent of all cancer-related deaths.

Even if the FDA grants approval, Glaxo will face an uphill battle against Merck’s Gardasil, which has had the U.S. market to itself for the last three years. Besides an established brand, Gardasil also boasts an extra degree of protection against sexually transmitted diseases.

Gardasil and Cervarix both defend against HPV strains 16 and 18, which cause about 70 percent of cervical cancer cases. But Merck’s vaccine also defends against two other HPV types that cause 90 percent of genital warts, something Cervarix does not target.

Leerink Swan analyst Seamus Fernandez estimates Glaxo’s Cervarix will eventually make up 25-30 percent of the total market for HPV-blocking vaccines. Cervarix global sales were $231 million last year.

Even as the British drugmaker moves closer to competing in the U.S., Whitehouse Station, N.J.-based Merck is seeking approval to begin marketing Gardasil to boys and men.

The panel is scheduled to vote later Wednesday on Gardasil as a preventive measure against genital warts in males.